What is the maximum message size that SendMail can successfully receive and where would the bottlenecks be?

CentOS 5.x | SendMail 8.14

I'm curious - what is the largest message size that SendMail will successfully accept from an upstream source via SMTP? The tweaking config options page indicates that by default, confMAX_MESSAGE_SIZE is "infinite".

I understand that downstream MTAs have their own limits and it's not practical these days to send attachments to larger than, say, 25 MB.... but since sendmail doesn't have an upstream restriction by default, at what point is it conceivable to expect things like OutOfMemory errors? Are there other bottlenecks that affect SendMail's ability to receive really large messages?

Solution 1:

• IMHO network perspective suggests lower limits than host/server perspective. Do not look at large/huge messages from "normal day" perspective. Think about "bad days". Based on my personal experience large/huge messages may create huge problems in case of slow/congested/backup links or email loops. I also slightly dislike different limits for internal and Internet emails.

• I do hate downloading huge spam messages over mobile broadband in places/areas with slower link speed.